1. Field of the Invention
The present invention relates to a protecting apparatus for an injection type engine employing a liquefied petroleum gas (LPG) as a fuel, and more particularly to a fuel injection valve protecting apparatus for protecting a fuel injection valve in the case where an excessive driving current flows through the fuel injection valve or some kind of abnormality or another occurs, and a fuel pressure increase preventing apparatus for protecting a petroleum gas fuel supplying system.
2. Description of the Related Art
In a conventional LPG injection type engine, a fuel injection valve is provided with no protecting means or protecting mechanism against an abnormal current. Accordingly, in the case where an abnormal current such as an excessive current flows through the fuel injection valve, or some kind or another abnormality occurs therein, it is impossible to protect the fuel injection valve. In general, the fuel injection valve of the LPG injection type engine injects a petroleum gas fuel into an intake manifold from a fuel injection port by attracting a needle valve with a magnetic force generated by a coil to open the fuel injection port thereof. However, in the case where an excessive current flows through the coil, there is a risk that the coil abnormally generates heat and a resin part of the fuel injection valve such as a bobbin around which the coil is wound is damaged.
Further, in the LPG injection type engine, in the case where a vaporizer for vaporizing a liquefied petroleum gas breaks down, there is a possibility that a pressure applied to the fuel injection valve becomes abnormally high. As the conventional LPG injection type engine is provided therein no mechanism or apparatus for inhibiting such a pressure increase, there is a risk that a part such as a pressure sensor or the like breaks down and an engine malfunction occurs due to the abnormal pressure increase.
Incidentally, Japanese Patent Laid-Open Publication No. 5-214937 discloses a technique that in order to prevent an after burn and a back fire caused by improperly supplying a gas fuel just before an engine stop during engine stalling or at a time of an engine start failure in a gas fuel engine using a hydrogen gas or the like, a fuel shutoff valve is provided on a downstream side of a flow regulating valve in a fuel passage, wherein an intake state is detected by a venturi of an intake manifold or the like, so that the fuel shutoff valve is closed before the engine stop. However, this technique is intended to prevent the after burn and the back fire at a time of the engine start failure and the engine stalling and is not relevant to the fuel gas pressure increase in the LPG injection type engine which is aimed at by the present invention, that is, this technique does not automatically inhibit the fuel gas pressure increase at the breakdown of the vaporizer or the like.